According to National Fire Protection Agency regulations covering aircraft refueling, a deadman control must be used with the valve that controls the flow of fuel to an aircraft, and deadman controls shall be designed to preclude defeating their intended purpose. Further, the fuelling operator should monitor the panel of the fuelling equipment and the aircraft control panel during pressure fuelling or should monitor the fill port during overwing fuelling. According to the regulations, use of any means that defeats the deadman control shall be prohibited. A deadman switch should be used with fuel flow control valves such as a hydrant pit valve, a tank outlet on a tank vehicle, a separate valve on the tank vehicle or on a hose nozzle for overwing service.
Under typical regulations, a deadman switch should be used when performing any pressure fueling or tender filling operation. Deadman switches are designed to safeguard against over filling circumstances or situations that may delay the suspension of fuel flow. Fuel flow stops when the deadman device is released. Ideally, a deadman switch should not be jammed or bypassed during any fuel transfer operation. Deadman switch types include the electromechanical deadman switch, pneumatic deadman switch (sometimes called the air deadman switch), and combination electromechanical/pneumatic types. The deadman switch is actuated, for example through being in the hands of the operator, during a refueling process.
However, a conventional equipment control system, such as a conventional deadman switch, provides no method of identifying the operator and so may be used by any person, even those not authorized or trained to use the equipment. Also, conventional equipment controls are susceptible to jamming or locking in an operating position. These conventional systems allow both authorized and non-authorized personnel to purposely jam existing deadman switches into an operating position.
There are also many other circumstances where an authorized person such as an authorized operator needs to be in proximity to the equipment or operation. These circumstances may include any hazardous operation (such as a fueling operation), operation of equipment, medical monitoring situations, operation of equipment requiring some kind of safety interlock system, and the like. Conventional equipment control methods do not attempt to identify an authorized operator.